This invention relates to reciprocating piston engines and more particularly to engines in which reciprocating pistons transmit their thrust to a drive shaft by means of rollers which engage a cam mounted on the drive shaft.
In one common type of reciprocating piston engine, pistons are connected through a connecting rod to a crank on a crank shaft. The piston moves in one direction in the cylinder as the crank shaft rotates through 180.degree. and moves in the opposite direction during the next 180.degree. of rotation. In a four cycle internal combustion engine, the crank shaft rotates sequentially through 180.degree. during an intake stroke of the piston, through 180.degree. during a compression stroke of the piston, through 180.degree. during a combustion or power stroke of the piston and through a final 180.degree. during an exhaust stroke of the piston. Each stroke of the piston is inherently confined to 180.degree. rotation of the crank shaft. Such an arrangement does not provide maximum efficiency in the engine cycle, particularly with relatively slow burning fuels.
In another type of reciprocating piston internal combustion engine, such as is illustrated in the U.S. Pat. No. 1,765,713, cylinders are arranged radially about a drive shaft. Each piston within a cylinder is attached to a roller which is held in contact with a first cam mounted on the drive shaft. Linkages and a second set of rollers riding on a second cam on the drive shaft hold the rollers attached to the pistons in contact with the first cam so that as the pistons reciprocate, the cam is caused to rotate to in turn rotate the drive shaft. In order to maintain the rollers attached to the piston in contact with the cam, the second cam has a different profile from the first cam. A modification of this type of engine is illustrated in U.S. Pat. No. 1,863,877 in which a spring loaded strap extends over sets of rollers to hold the rollers attached to the pistons in contact with the cam. The cam illustrated in this patent has major and minor diameters which are displaced from one another by less than 90.degree. so that the power and intake strokes of the piston occur over 35.degree. of shaft rotation and the compression and exhaust strokes of the pistons occur over 55.degree. of shaft rotation. This arrangement appears to provide less efficiency over conventional engines having a crank shaft for converting reciprocating motion to rotary motion since intake and power portions of the cycle take place over a smaller percentage of the total cycle than the compression and exhaust portions of the cycle. Furthermore, a complicated arrangement is required for holding the piston mounted rollers in contact with the cam.